Polyvinyl chloride-antimony oxide flame-retardant mixtures for cellulosic spinning dopes

ABSTRACT

THE PRESENT INVENTION RELATES TO CELLULOSIC COMPOSITIONS WHICH ARE CAPABLE OF BEING FORMED INTO FLAME-RETARDANT STRUCTURES, SUCH AS FIBERS, FILAMENTS, FILMS AND THE LIKE. THESE FLAME-RETARDANT CELLULOSIC COMPOSITIONS ARE PREPARED BY ADDING A FLAME-RETARDING AMOUNT OF A MIXTURE COMPRISED OF A VINYL CHLORIDE POLYMER AND AN ANTIMONY OXIDE TO CELLULOSIC SPINNING SOLUTIONS OR DOPES FOLLOWED BY THE COAGULATION OF THESE SOLUTIONS OR DOPES TO PRODUCE FLAME-RETARDANT CELLULOSIC SHAPED ARTICLES, SUCH AS FILAMENTS, FIBERS, FILMS AND THE LIKE.

United States Patent O POLYVINYL CHLORIDE-ANTIMONY OXIDE FLAME-RETARDANTMIXTURES FOR 'CEL- LULOSIC SPINNING DOPES Robert L. McClure,Elizabethton, Tenn., assignor to Beaunit Corporation, New York, N.Y. NoDrawing. Filed June 20, 1968, Ser. No. 738,399 Int. Cl. D01f 3/04 US.Cl. 260-174 2 Claims ABSTRACT OF THE DISCLOSURE The present inventionrelates to cellulosic compositions which are capable of being formedinto flame-retardant structures, such as fibers, filaments, films andthe like. These flame-retardant cellulosic compositions are prepared byadding a flame-retarding amount of a mixture comprised of a vinylchloride polymer and an antimony oxide to cellulosic spinning solutionsor dopes followed by the coagulation of these solutions or dopes toproduce flame-retardant cellulosic shaped articles, such as filaments,fibers, films and the like.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to the preparation of cellulosic shaped articles, such asfilaments, fibers, films and the like having improved flame-retardantproperties.

(2) Description of the prior art Cellulosic compositions, particularlyfiber-forming compositions, possess a number of characteristics whichrender them of substantial 'value for a variety of textile and otheruses. However, in order to use these cellulosic compositions in manyapplications it is necessary that they be modified or treated to providethem with flameretarding properties or characteristics. Conventionalprocedures for imparting flame-retardant properties to shaped articles,such as fibers and filaments, of cellulose or cellulose derivativesinvolve impregnating or coating the cellulose containing films offilaments, fibers or fabrics formed therefrom with a suitableflame-retardant composition followed by drying or curing. Suchflame-retardant treatments alter the physical properties of the treatedmaterials such as the hand or feel of the treated material. Thesefinishes are generally easily removed by laundering, dry cleaning orleaching in water and, therefore are ineffective after short periods ofnormal use. For these reasons, such treated fibers, filaments, andfabrics have found only limited commercial acceptance in the textiletrade.

SUMMARY OF THE INVENTION The present invention provides cellulosicarticles, such as films, fibers, filaments, or fabrics therefrom, havingexcellent flame-retarding properties and is accomplished by theincorporation of a flame-retarding amount of a mixture comprising avinyl chloride polymer and an antimony oxide in conventional cellulosicspinning solutions followed by the formation of shaped articles, such asfilaments, fibers, films and the like from these solutions.

The cellulosic spinning solutions of this invention generally comprise aconventional cellulosic spinning solution or dope, such as acuprammonium cellulose spinning solution or dope, a viscose spinningsolution or dope, or a cellulose ester spinning solution or dope, whichcontains a mixture comprising a vinyl chloride polymer and an antimonyoxide in an amount sufiicient to impart fireretardant properties to thestructure obtained by co- Patented Apr. 20, 1971 agulating such spinningsolutions or dopes in conventional coagulating baths followed byleaching and drying.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cellulosic spinningsolutions or dopes of this invention are intended to includecuprammonium and viscose spinning solutions as well as cellulose esterspinning solutions. These spinning solutions will include solutions ofcellulose or the reaction products of cellulose and ammonia-coppercomplexes in an aqueous solution of an ammonia-copper complex as, forexample, cuprammonium spinning solutions or dopes; solutions ofcellulose xanthate in "Water and aqueous alkalis such as aqueous sodiumhydroxide solution as, for example, viscose syrups and dopes; organicacid or anhydride derivatives of cellulose such as cellulose acetatesolutions, cellulose propionate solutions or other solutions of aproduct obtained by reacting cellulose with an organic acid oranhydride; and the like. The preparation of the cellulosic spinningsolutions of this invention are conventional to those skilled in theart. The preparation of cuprammonium spinning solutions, viscosespinning solutions, and cellulose acetate spinning solutions aredescribed generally in The Rayon Industry (1929), published by D. VanNostrand Company, New York, N.Y., on pages 523-543, 436-522, and 559-580respectively and in Man-Made Fibers by R. W. Moncrief, published by JohnWiley & Sons, Inc., New York, N.Y. (1966), on pages 196-203, 138-195,and 204-233 respectively. The use of the cuprammonium spinning solutionsand the preparation of flameretardant cuprammonium rayon articles arepreferred for the purposes of this invention. Shaped articles preparedfrom viscose spinning solutions are normally discolored because of sidereactions which take place between the antimony oxide and the sulfur orsulfides present in the conventional cellulose xanthate or viscosespinning solutions. In addition, the normal funnel type spinning usinglarge hole spinnerets and used in the preparation of cuprammonium rayonarticles appears best suited for use in carrying out the purposes ofthis invention.

The spinning solution used in the preferred cuprammonium process isobtained by dissolving cellulose in a cuprammonium solvent which isessentially an aqueous solution of copper and ammonia characterized bythe cuprammonium ion. This aqueous solvent must contain specificquantities or concentrations of copper in cupric form and ammonia inorder for the cellulose to remain dissolved therein. These amounts willnormally run from about 2 to 4 percent of copper and from about 4 to 7percent of ammonium. It is generally recognized that the cuprammoniumion of the solvent forms a complex with the cellulose to give a solublecopper-ammonia-cellulose compound. This cuprammonium cellulose solutioncan then be extruded or spun, e.g., as filaments or the like into anaqueous spin bath or coagulating bath. The aqueous coagulating bath,which may be neutral or basic, essentially functions as a diluent tolower the concentration of ammonia and copper to the point where thecellulose tends to harden or coagulate in the form extruded. The spinbath may also serve to remove some of the solvent from the precipitatedfilaments or the like.

Although it is possible to use water alone as the coagulating bath forthe spun filaments, it has been a more common procedure to employ analkaline coagulating bath, in order to obtain a good coagulation andbetter qualities in the finished product. After coagulation, there isbelieved to be formed a copper-alkali cellulose material which can bedecomposed to fully regenerate the cellulose by subsequent treatment inan acid bath. In

some cases, it has been found advisable to treat the coagulated materialfrom the alkaline bath with water alone in order to hydrolyticallydecompose the copper-alkalicellulose prior to treatment with acid. Theacid treatment then serves to remove copper hydroxide when taken inconjunction with subsequent washing to remove salts and adhering acid.After washing, the cellulose article is dried and stored in any suitablemanner.

With respect to the production of filaments, the cuprammonium spinningsolution is ordinarily extruded into a funnel or bath through which theaqueous coagulating medium is circulated, and the cellulose of thecoagulated filament is then regenerated by treatment in an acid bath,Washing and drying. A portion of the ammonia and copper is removedduring coagulation, essentially by dilution of the spinning solution asnoted above, and the ammonia and copper remaining with the celluloseafter cagulation are separated during the acid treatment and subsequentwashing.

The various spinning solutions or dopes used for the purposes of thepresent invention may contain varying amounts of cellulose or cellulosederivatives, depending upon the particular spinning solution used andthe end use of the product desired, such as in spinning filaments,preparing stable fibers, casting films and coatings, and the like.Generally, they will contain from about 2 to 40 percent by weight ofcellulose or cellulose derivative. The cuprammonium and viscose spinningsolutions or dopes of this invention will normally contain about 2 topercent by weight of the cellulose or cellulose derivative and thecellulose ester spinning solutions of this invention will normallycontain about to percent by weight of the cellulose or cellulosederivative.

The spinning solutions or dopes described above may contain conventionaladditives such as delustering agents, cationic and non-ionic surfaceactive agents, dyes, pigments, stabilizers and the like, in addition tothe specific additive mixtures of this invention.

The amount of flameretarding mixture used may vary. Broadly, it has beenfound that about 10 to 100 parts by weight of flame-retarding mixturemay be used, based on 100 parts by weight of cellulose or cellulosederivative, in the spinning solution or dope to obtain a shaped articlewhich has sufficient strenght to be useful as a filament, fiber, orfabrics therefrom. It is preferred that about 10 to parts by weight ofthe flame-retarding mixture be used, based on 100 parts by weight ofcellulose or cellulose derivative in the spinning solution or dope. Theresulting shaped article prepared from these spinning solutions shouldhave essentially the same weight distribution as the spinning solutionwith the flameretarding mixture distributed uniformly throughout thecellulosic article. It has been found that at least percent of theflame-retarding mixture is retained in the article produced. The exactamount will depend upon the solubility of the mixture in the spinningsolution.

The flame-retarding mixture of this invention may be composed of fromabout 20 to 90 percent by weight of a vinyl chloride polymer and fromabout 10 to percent by weight of an antimony oxide. Preferably, theflameretarding mixture in the shaped articles will contain from about 50to 75 percent by weight of a vinyl chloride polymer and from about 25 to50 percent by weight of an antimony oxide. This combination of a vinylchloride polymer and an antimony oxide produces a synergistic effect inwhich the total flame retardance is greater than the sum of theindividual components.

The vinyl chloride polymers which form an essential part of theflame-retardant mixture of this invention include homopolymers, such aspoly(vinyl chloride) and poly (vinylidene chloride), and copolymers ofvinyl chloride or vinylidene chloride with other polymerizableolefinically unsaturated compounds, such as vinyl acetate, methylacrylate, methyl methacrylate, methyl chloroacrylate, acrylonitrile, andthe like, wherein the vinyl chloride or vinylidene chloride is presentin amounts of at least about 50 percent by weight. Preferably, the vinylchloride polymers used are poly(vinyl chloride), poly (vinylidenechloride), or copolymers of vinyl chloride or vinylidene chloride inwhich the vinyl chloride or vinylidene chloride is present in amounts ofat least about percent by weight.

The antimony oxides which form an essential part of the flame-retardantmixture of this invention include antimony trioxide, antimonytetraoxide, and antimony pentoxide. Preferably, antimony trioxide willbe used for the purposes of this invention.

The regenerated cellulosic structures of this invention are prepared byshaping the cellulosic spinning solutions or dopes containing theflame-retarding mixtures of this invention to the desired form and thensubjecting the shaped solution or dope to a coagulating bath whereby thecellulose or cellulose derivative is precipitated. The spinningsolutions or dopes containing the vinyl chloride polymer-antimony oxidemixtures of this invention coagulate and harden in the coagulatingmedium. The resulting article may then be washed and dried. Thecuprammonium articles may be decopperized with dilute sulfuric acidsolutions and washed with water. The cellulosic structures obtained havethe flame-retarding mixture of this invention uniformly dispersedtherein and have ex cellent flame-retarding properties after repeatedwashings or repeated dry cleanings.

A variety of fire-retardant articles, such as filaments, fibers, films,coatings, and the like may be prepared from the spinning solutions ofthis invention in any conventional manner. Preferably, filaments andfibers are prepared from the spinning solutions by extruding thecellulosic spinning solution or dope through orifices in a spinneretinto a coagulating medium, such as a bath, to regenerate the celluloseor cellulose derivative in filament form, after which the filaments maybe collected on spools, or in centrifugal pots, or in any well knownmanner. The filaments are then processed in any normal manner. It hasbeen found that it is preferable to use conventional funnel typespinning in preparing the filaments of this invention in order to avoidany possible clogging of spinneret orifices.

The filaments, staple fibers, and the like which may be prepared fromthe compositions of this invention may be processed into knit or wovenfabrics by conventional operations, Filaments and the like may be sizedand then woven or knitted into fabrics, while the staple fibers and thelike are converted into threads or yarns which then may be sized andWoven or knitted into fabrics. These fabrics have outstandingflame-retarding properties and retain these properties after repeatedwashings or after being subjected to repeated commercial dry cleanings.The filaments, staple fibers, and the like of this invention may also beblended with other textile yarns or fibers and knitted or Woven byconventional methods into fabrics having good flame-retardingproperties.

The following examples are presented as a further disclosure andillustration of the improved products of this invention and are notintended as a limitation thereof. All parts, proportions and percentagesare by weight otherwise indicated.

The flame test method used in the examples is the A.A.T.C.C. (AmericanAssociation of Textile Colorists and Chemists) Test Method #34-1966entitled Fire Resistance of Textile Fabrics.

EXAMPLE 1 A typical preparation of a flame-retarding mixture of thisinvention: To a stirred solution of 280 grams of high viscositycarboxymethyl cellulose a dispersing acid) and 1300 grams ofoctylphenoxypolyethoxyethanol (a surface active agent) in 30 liters ofwater, there was added 168 lbs. of a 50 percent aqueous dispersion of avinylidene chloride-vinyl chloride copolymer containing less than aboutpercent of vinyl chloride and of about 70 percent chloride content, 56lbs. of a 50 percent aqueous slurry of antimony trioxide of about 1.5micron particle size and 12 liters of a 26 percent aqueous solution ofammonium hydroxide. This mixture was then diluted to a volume of about280 liters by the addition of water to produce a stock solution of about182 grams per liter of solids which constains about 136 grams per literof the vinyl chloride polymer and about 45 grams per liter of antimonytrioxide.

EXAMPLE 2 The flame-retarding mixture prepared in Example 1 is added toa conventional cuprammonium spinning solution composed of about 8 /2percent of cellulose at a ratio to produce a spinning solutioncomprising about 5.66 percent of cellulose and about 2.83 percent of theflame-retarding mixture. This modified spinning solution was then castinto strong, white film containing about 66 /3 parts of cellulose, about25 parts of the vinylidene chloride-vinyl chloride copolymer and 8 /3parts of antimony trioxide. This film was subjected to the standardA.A.T.C.C. flame test and it was observed that the afterflame time wasless than one second.

Film prepared in a similar manner as above and containing about 72.8parts of cellulose and about 27.2 parts of the vinylidene chloridelvinylchloride copolymer was subjected to the same flame test and burnedcompletely.

Film prepared in a similar manner as above and containing about 88 partsof cellulose and about 12 parts of antimony trioxide was subjected tothe same flame test and it was observed that the afterflame time wasmore than two seconds as called for by this test.

EXAMPLE 3 The flame-retarding mixture prepared in Example 1 is added toa conventional cuprammonium spinning solution composed of about 8 /2percent of cellulose at a ratio to produce a spinning solutioncomprising about 5.66 percent of cellulose and about 2.83 percent of theflameretarding mixture. This modified spinning solution is then extrudedinto a conventional coagulation bath to produce strong, white filamentcontaining about 66% percent of cellulose and about 33 /3 percent of theflame-retarding mixture. This filament had a hand or feel substantiallyidentical to that of unmodified cuprammonium rayon yarn.

Woven fabric prepared from the filaments prepared above was subjected tothe standard A.A.T.C.C. flame test and it was observed that theafterflame time was less than one second.

A woven fabric prepared from unmodified cuprammonium rayon yarn burnedcompletely when subjected to the above test.

EXAMPLE 4 A cuprammonium spinning solution containing about 6 percent ofcellulose and about 33 percent, based on the cellulose content of thesolution, of a flame-retarding mixture of about 75 percent of thevinylidene chloride-vinyl chloride copolymer of Example 1 and about 25percent of antimony trioxide of about 1.5 micron average particle size,was extruded through a spinneret containing 225 holes, each having adiameter of about 0.8 mm., into an aqueous coagulation bath followed byan aqueous bath containing about 4 percent sulfuric acid at a ratesufficient to produce 400/225 cuprammonium rayon filament yarn. Thecoagulation yarn was collected on a reel, tied into a skein, andsubjected to conventional washing and drying procedures. The resultantyarn which had a hand or feel substantially identical to that ofunmodified cuprammonium rayon yarn was woven into a fabric and subjectedto the standard A.A.T.C.C. flame test whereupon it was observed that theafterflame time was less than one second.

6 EXAMPLE 5 Following the procedure described in Example 4, acuprammonium spinning solution containing about 6 percent of celluloseand about 25 percent, based on the cellulose content of the solution, ofthe flame-retarding mixture of Example 4 was spun into cuprammoniumrayon yarn having a hand or feel substantially identical to that ofunmodified cuprammonium rayon yarn. This yarn was woven into fabric andsubjected to the standard A.T.T. C.C. flame test. It was observed thatthe afterflame time was less than one second.

EXAMPLE 6 Following the procedure described in Example 4, a cuprammoniumspinning solution containing about 6 percent of cellulose and about 20percent, based on the cellulose content of the solution, of theflame-retarding mixture of Example 4 was spun into cuprammonium rayonyarn having a hand or feel substantially identical to that of unmodifiedcuprammonium rayon yarn. This yarn was woven into fabric and subjectedto the standard A.A.T. C.C. flame test. It was observed that theafterflame time was less than one second.

EXAMPLE 7 A conventional viscose spinning solution was preparedcontaining about 66 /3 parts of cellulose, about 25 parts of thevinylidene chloride-vinyl chloride copolymer of Example 1, and about 8/3 parts of antimony trioxide. Film was cast from this solution in aconventional manner. This film was an orange-brown color but it wasobserved that the afterflame time for this film was less than one secondwhen it was subjected to the standard A.A.T. C.C. flame test.

EXAMPLE 8 A conventional cellulose acetate spinning solution wasprepared containing about 66 /3 parts of cellulose acetate, about 25parts of the vinylidene chloride-vinyl chloride copolymer of Example 1,and about 8 /3 parts of antimony trioxide. Strong, white film was castfrom this solution in a conventional manner. This film was subjected tothe standard A.A.T.C.C. flame test and it was observed that theafterflame time was less than one second.

EXAMPLE 9 A modified spinning solution prepared in a manner identical tothat followed in Example 3 was extruded in a regular cuprammonium funnelusing a 2000 hole, 200 micron viscose spinneret to produce a 1000/2000/0filament yarn comprising about 66 /3 parts of cellulose, 25 parts of thevinylidene chloride-vinyl chloride copo ymer of Example 1, and 8 /3parts of antimony trioxide. Acceptable filament was obtained althoughsome orifice clogging was observed. This filament was subjected to thestandard A.A.T.C.C. flame test and it was observed that the afterflametime was less than one second.

EXAMPLE 10 A woven fabric made from rayon yarn was dipped into anaqueous dispersion comprising about grams per liter of solids of whichabout 75 percent is the vinylidene chloride-vinyl chloride copolymer ofExample 1 and about 25 percent is antimony trioxide. The coated fabricwas squeezed and dried to provide a pickup of about 10 percent of themixture on the fabric. The coated fabric was stiff and had a hand orfeel considerably less desirable than the uncoated yarn. This coatedfabric was subjected to the standard A.A.T.C.C. flame test and it wasobserved that the afterflame time was more than two seconds as calledfor by this test. A

Higher concentrations of additive may be used to provide a coated fabrichaving improved flame-proofing properties. However, these fabrics wouldhave a very poor hand or feel and the flame-proofing properties woulddeteriorate with repeated launderings or dry cleanings.

It is understood that changes and variations may be made in the presentinvention by one skilled in the art without departing from the spiritand scope thereof as defined in the appended claims.

What is claimed is:

1. Regenerated cellulose filaments having been coagulated from acuprammonium cellulose spinning solution and having dispersed thereinfrom about 10 to 100 parts, based on 100 parts of cellulose present, ofa flame-retarding mixture comprised of from about 20 to 90 percent byweight of a vinyl chloride polymer selected from the group consisting ofpoly(vinyl chloride), poly(vinylidene chloride), and copolymers of vinylchloride or vinylidene chloride with other polymerizable olefinicallyunsaturated compounds in which the vinyl chloride or vinylidene chlorideis present in amounts of at least 50 percent by weight and from about 10to 80 percent by weight an antimony oxide.

2. The regenerated cellulose filaments of c aim 1 wherein theflame-retarding mixture is comprised of from UNITED STATES PATENTS3,235,642 2/1966 Blomberg 264182 2,591,368 4/1952 McCarthy 260-172,816,004 12/ 1957 Rossin et al. 264-188 3,243,391 3/1966 Wagner 260-453,277,226 10/1966 Bockno et al 2'6419 8 3,300,423 1/ 1967 Borown et al.26017 WILLIAM SHORT, Primary Examiner L. M. PHYNES, Assistant ExaminerUs. 01. X.R. 26017; 264-199

